Realization of a three-dimensional photonic topological insulator

Yang, Yihao; Gao, Zhen; Xue, Haoran; Zhang, Li; He, Mengjia; Yang, Zhаoju; Singh, Ranjan; Chong, Yidong; Zhang, Baile; Chen, Hongsheng

doi:10.1038/s41586-018-0829-0

Cited by 323 publications

(197 citation statements)

References 37 publications

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“…Near such a point, the Bloch waves are governed by the same Dirac Hamiltonian that describes a two-component massless relativistic fermion [1][2][3] . It is well known that the bandstructure of the 2D material graphene [1][2][3] possesses Dirac points at the two inequivalent corners of its hexagonal Brillouin zone (BZ), and similar pairs of Dirac points have been realized in optical lattices [4][5][6] as well as classical acoustic [7][8][9] , photonic [10][11][12][13][14][15] , and plasmonic 16,17 structures. In 2D systems preserving time-reversal symmetry (T), Dirac points necessarily occur in pairs 18 .…”

Section: Introductionmentioning

confidence: 99%

Observation of an unpaired photonic Dirac point

et al. 2020

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At photonic Dirac points, electromagnetic waves are governed by the same equations as twocomponent massless relativistic fermions. However, photonic Dirac points are known to occur in pairs in "photonic graphene" and other similar photonic crystals, which necessitates special precautions to excite only states near one of the Dirac points. Systems hosting unpaired photonic Dirac points are significantly harder to realize, as they require broken time-reversal symmetry.Here, we report on the first observation of an unpaired Dirac point in a planar two-dimensional photonic crystal. The structure incorporates gyromagnetic materials, which break time-reversal symmetry; the unpaired Dirac point occurs when a parity-breaking parameter is fine-tuned to a topological transition between a photonic Chern insulator and a conventional photonic insulator phase. Evidence for the unpaired Dirac point is provided by transmission and field-mapping experiments, including a demonstration of strongly non-reciprocal reflection. This photonic crystal is suitable for investigating the unique features of two-dimensional Dirac states, such as one-way Klein tunneling.

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Section: Introductionmentioning

confidence: 99%

Observation of an unpaired photonic Dirac point

et al. 2020

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“…Topological photonics has arrested a great deal of interest with intriguing optical phenomena associated with the topological edge states (TESs) . Nontrivial TESs have been well revealed in two‐dimensional (2D) photonic topological insulators, which demonstrated very good robustness to structural defects or scatterers with one‐way propagations .…”

Section: Introductionmentioning

confidence: 99%

Robust and Broadband Optical Coupling by Topological Waveguide Arrays

Song

Sun

Chen

et al. 2020

Laser & Photonics Reviews

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Photonic topological states have been exploited to give rise to robust optical behaviors that are quite insensitive to local defects or perturbations, which provide a promising solution for robust photonic integrations. Specifically, for example, optical coupling between waveguides is a universal function in integrated photonics. However, the coupling performance usually suffers from high structure‐sensitivity and challenges current manufacturing for massive production. Here, the topological edge state in a finite Su–Schriffer–Heeger modeled optical waveguide array is explored and robust optical coupling (e.g., directional coupling and beam splitting) is demonstrated, which is quite insensitive to structural variations. It is experimentally proved that even a large discrepancy (21–26% structural deviation) in silicon waveguides gaps has little influence on optical coupling (>90% performance), while conventional counterparts totally break down. Moreover, thanks to such a topological design, the devices show much broader working bandwidth (≈10 times performance improvement) than the conventional ones, greatly favoring the photonic integrations. This work would inspire new families of optical devices with robust and broadband properties that can excite more interesting and useful exploration in both fields, and possibly open a new avenue toward topological devices with unique properties and functionalities.

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“…Recently, numerous distinct topological states have been demonstrated in classical wave systems 18,19 such as photonic crystals [20][21][22][23][24][25][26][27][28] and phononic crystals 29 8 and photonic systems 28 .…”

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confidence: 99%

Symmetry-enforced three-dimensional Dirac phononic crystals

Cai

Qiu

et al. 2020

Light Sci Appl

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Dirac semimetals, the materials featured with discrete linearly crossing points (called Dirac points) between four bands, are critical states of topologically distinct phases.Such gapless topological states have been accomplished by a band-inversion mechanism, in which the Dirac points can be annihilated pairwise by perturbations without changing the symmetry of the system. Here, we report an experimental observation of Dirac points that are enforced completely by the crystal symmetry, using a nonsymmorphic three-dimensional phononic crystal. Intriguingly, our Dirac phononic crystal hosts four spiral topological surface states, in which the surface states of opposite helicities intersect gaplessly along certain momentum lines, as confirmed by our further surface measurements. The novel Dirac system may release new opportunities for studying the elusive (pseudo)relativistic physics, and also offer a unique prototype platform for acoustic applications.

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Realization of a three-dimensional photonic topological insulator

Cited by 323 publications

References 37 publications

Observation of an unpaired photonic Dirac point

Observation of an unpaired photonic Dirac point

Robust and Broadband Optical Coupling by Topological Waveguide Arrays

Symmetry-enforced three-dimensional Dirac phononic crystals

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